This invention relates to pyrazolone magenta dye-forming couplers having a particular thio coupling-off group that enables improved photographic properties and to photographic materials and processes comprising such couplers.
In color photographic silver halide materials and processes pyrazolone couplers comprising arylthio coupling-off groups have provided magenta dye images having useful properties. Examples of such compounds are described in, for example, U.S. Pat. No. 4,413,054, Japanese published patent application 60/057839, U.S. Pat. Nos. 4,900,657 and 4,351,897. An example of such a pyrazolone coupler described in, for example, U.S. Pat. No. 4,413,054 is designated herein as comparison coupler C-1 and is represented by the formula: ##STR2##
Coupler C-1 has not been entirely satisfactory due to the formation of undesired stain in a color photographic silver halide element upon exposure and processing and because it does not provide the desired image-dye density upon rapid machine processing. The coupler C-1 does not achieve full dye density, especially when the exposed color photographic element is machine processed without the presence of Lippman fine grain silver halide being present in the photographic element. It has been desirable to reduce or avoid the need for added Lippman fine grain silver halide without diminishing dye density in the processed color photographic silver halide element.
Another example of a pyrazolone coupler known to the art is described in U.S. Pat. No. 4,853,319 is designated herein as comparison coupler C-2 and is represented by the formula: ##STR3##
The presence of an acylamine group in the ortho position on the phenylthio coupling-off group of coupler C-2 has provided advantageous properties. This coupler does not require Lippman fine grain silver halide in order to obtain adequate dye density upon rapid machine processing. However, the coupling activity of both couplers C-1 and C-2 is unacceptably reduced in the presence of polyvalent cations, especially calcium ion, which leads to a reduction of the color density of the green record. Further, the hue of the resultant dyes from these two couplers is too hypsochromic to give good color reproduction. Another problem of certain types of arylthiopyrazolone couplers is extremely poor solubility in photographic coupler solvents. The poor solubility necessitates the use of auxiliary solvents which then have to be removed through an undesirable additional washing step.
U.S. Pat. No. 4,942,116, to Renner (Counterpart to DE 3,730,557) teaches 3 anilino pyrazolones with a broad array of arylthio coupling-off groups containing an alkyl substituent in the ortho position. The products are, however, concerned with light stability of dye images in color prints and not the features described for this invention. Moreover, the only examples that provide a sigma of 1.3 as provided for herein utilize cyanide as an electron withdrawing agent. Cyanide substituents are not within this invention because of their notorious light instability (see for example EP 439,069).
U.S. Pat. No. 4,740,438 teaches the use of organic disulfides as image dye light stabilizers with couplers such as C-10. This type of coupler is characterized by having a 5-sulfamoyl ballast in the 3-anilino ring of the pyrazolone. As demonstrated in the examples, the dye from this coupler has unacceptable hue for adequate color reproduction, especially that of reds. ##STR4##
Another type of coupler that has been considered is one having a pentachloro-substitution on the N phenyl ring (U.S. Pat. No. 4,876,182). While such materials provide advantageous properties they are not preferred because rings containing more than 3 chloro substituents present laborious and costly administrative efforts relative to disposal.
It has been desired to provide a new pyrazolone coupler having an arylthio coupling-off group in a color photographic silver halide element and process which is capable of forming a magenta dye image of good dye hue and stability, with high dye yield based on rapid machine processing, and with reduction or omission of Lippman fine grain silver halide in the element. Also, it has been desired to provide such 2-equivalent pyrazolone couplers with adequate solubility/dispersibility characteristics, so that the couplers can be easily incorporated into color photographic silver halide elements. Further, it has been desired to reduce the sensitivity of arylthiopyrazolone couplers toward changes in polyvalent cation levels, especially calcium ion, in the processing of photographic elements. Additionally, it has been desired to provide a multilayer photographic element containing such a coupler which exhibits improved acutance and granularity.